1. Field of the Invention
The present invention relates generally to an information storage apparatus for sharing data among electronic devices such as information processing devices and an information processing apparatus using the information storage apparatus, and more particularly to a write prohibit mechanism for protecting internal data in an external storage apparatus.
2. Description of the Related Art
In a conventional method of sharing data among information processing devices, an attachable/detachable external storage apparatus in which data can be written is generally used. This type of external storage apparatus is normally provided with a write prohibit mechanism for protecting precious internal storage data from being erroneously erased.
In a typical write prohibit mechanism, for example, as used in a magnetic tape or a floppy disk, the shape of a portion of a casing of the external storage apparatus is made changeable and the change in shape is optically or mechanically detected on the information processing device side.
FIGS. 5A and 5B illustrate an example of the conventional write prohibit mechanism which is employed, for example, in a 3.5 inch floppy disk.
A floppy disk 1 has, in proper places, a sliding shutter 2 for data write/read, a bearing unit 3 for rotating a built-in magnetic disk, a label attachment section 4 on which a label indicating a title, etc. is attached, and a write protect tab 5. As is shown in FIGS. 5A and 5B, the write protect tab 5 comprises a slider 5a and an opening window 5b which is closed and opened in accordance the movement of the slider 5a.
Specifically, in the write prohibit mechanism using the write protect tab 5, the two shapes of the window 5b, i.e. the open shape and closed shape, which is determined by the movement of the slider 5a, are detected by means of a contact switch, etc. Thus, the write permit state and the write prohibit state can be discriminated on the information processing device side.
In another data write prohibit mechanism, an electric write path is cut off by a microswitch, as in a memory card in which data write is electrically effected.
In the write prohibit mechanisms, a change in physical shape is made mechanically. Therefore, there is an advantage in that the write permit state or write prohibit state can be recognized by the eye.
In each mechanism, however, the external storage apparatus needs to have certain dimensions and thickness.
On the other hand, there is a method in which a write prohibit state is stored as internal data in an external storage apparatus. Advantageously, this method can be applied to any type of external storage apparatus, irrespective of the size and thickness thereof.
In this method, however, the write permit state or write prohibit state cannot be recognized until the external storage apparatus is mounted in an information processing device and actually operated.
As has been described above, in the prior art, the external storage apparatus needs to have certain dimensions and thickness in order that one can recognize the write prohibit state.